1. Field of the Invention
The present invention relates to the construction of an extremely-small-swing working machine, constituting a working arm device by installing a working attachment on a boom-and-arm mounted on a swing table, enabling extremely-small swing in such a way that the boom-and-arm does not get out of the maximum-diameter swing circumference of the swing table in plan view when the boom-and-arm is folded to an upright state, and also enabling to offset the working attachment to left and right by turning the boom to left and right on the way thereof.
2. Background Art
Known as extremely-small-swing working machine constituted by installing a working attachment to a boom-and-arm mounted on a swing table disposed on a travelling machine is a swing excavator constituting a backhoe device by installing a bucket as working attachment, etc., for example. Moreover, also known to the public is a machine enabling to offset the attachment by turning the boom to left and right on the way thereof.
Explanation will be given, with reference to FIG. 40 to FIG. 49, on a swing excavator comprising a backhoe as an example of conventional swinging machine. As shown in FIG. 40 and FIG. 41, at the top of a travelling device 81 is slewably mounted a swing table 84, and at the top of the swing table 84 is provided an operator""s cab 89 in which the operator""s seat is covered by a cabin or a canopy, etc. The description regarding orientation and position hereafter will be given with reference to the orientation and position of the operator""s cab 89.
On one side of the operator""s cab 89 is mounted a first boom section 90 in a way to turn freely from front bottom to rear top, at the tip of the first boom section 90 is mounted a second boom section 91 in a way to turn freely to left and right, on the second boom section 91 is mounted a third boom section 92 in a way to turn freely, on the third boom section 92 is mounted an arm 93 in a way to turn up and down in the longitudinal direction, and at the tip of the arm 93 is mounted a bucket 94, which is a working attachment, in a way to turn up and down in the longitudinal direction, to constitute a backhoe device 85, making it possible to move (offset) the arm 93 and the bucket 94 by turning the second boom section 91 to left and right, and execute excavation work of street drain, etc.
The first boom section 90 is turned from front bottom to rear top by telescopic motion of a boom cylinder 97, the arm 93 is turned up and down by telescopic motion of an arm cylinder 98 interposed between the arm 93 and the third boom section 92, and the bucket 94 is turned up and down by telescopic motion of a bucket cylinder 99 interposed between the arm 93 and the bucket 94.
Moreover, the second boom section 91 is turned to left and right by telescopic motion of an offset cylinder 100 interposed between the first boom section 90 and the second boom section 91, while, on the other hand, between the first boom section 90 and the third boom section 92 is interposed a connecting rod 101, forming a link parallel to the second boom section 91, and the third boom section 92, the arm 93 and the bucket 94 are offset to left and right in a state parallel to the first boom 90.
Furthermore, the axis of the lower rotating shaft 95, connecting between the first boom section 90 and the second boom section 91, and the axis of the upper rotating shaft 96, connecting between the second boom section 91 and the third boom section 92, are disposed to be mutually parallel and, as shown in FIG. 40, the lower rotating shaft 95 is constructed in such a way that the end part on the side closer to the arm 93 of this lower rotating shaft 95 is placed at a position lower than the end part on the opposite side (namely, sloped downward in the forward direction), when the first boom section 90 is raised to its highest position.
The backhoe device 85 indicated in FIG. 40 is in a state in which the arm 93 is folded to the fullest extent, when the first boom section 90 is raised to its highest position (placed at the limit position of rear upward turn), and the rear end of the backhoe device 85 does not protrude backward from the rear end of the swing table 84, making it possible for the rear end of the backhoe device 85 to turn in the swing circle with maximum diameter of the swing table 84 in plan view, when the swing table 84 is turned in that state, and thus enabling extremely-small swinging with no fear of hitting against any obstacle. This state of backhoe device 85 will be called a state stored for extremely-small swing.
A locus 77 in FIG. 40 is the locus in which the tip part of the bucket 94 passes, with an up-down turning operation of the first boom section 90, the arm 93 and the bucket 94. This downward locus of the bucket 94 is produced when the bucket 94 is turned downward in the forward direction from the state in which it is folded to the fullest extent in said state stored for extremely-small swing, the arm 93 is also turned in the forward direction, and the bucket 94 is folded upward in the backward direction. As shown in the illustration, the locus 77 of the bucket 94 overlaps with the operator""s cab 89 in side view, at some positions. Basically, the bucket 94 turns by the side of the operator""s cab 89 when no offsetting is made, and there is no mutual interference between the two. However, in the case where the breadth of the bucket 94 is increased for an excavation work with a large breadth, etc., there are cases where interference is produced between the bucket 94 and the operator""s cab 89 at points where the locus 77 overlaps with the operator""s cab 89, and such interference must be avoided.
And, in the case where the first boom section 90 is raised to its highest position, the end closer to the arm 93 (front end) of the lower rotating shaft 95 comes to a position lower than the end on the opposite side (rear end) and, for that reason, as the second boom section 91 turns around the lower turning shaft 95, the bucket 94 moves to left and right and, as shown in FIG. 42, moves backward by a distance equal to the dimension V, namely in the direction coming closer to the operator""s cab 89. The locus of the tip of the bucket 94 comes more in the backward direction than the locus 77 at a time without offset in FIG. 40.
It is when the bucket 94 is offset to the operator""s cab 89 that a problem of interference with operator""s cab 89 is posed. Even if the locus of the tip of the bucket 94 at a time of offset agrees with the locus 77, the bucket 94 cannot be positioned at points where the locus 77 overlaps with the operator""s cab 89, in FIG. 40. In addition, since the actual locus at a time of offset is further in the backward direction than the locus 77, there are cases where interference is produced with the operator""s cab 89 if any offsetting is made.
Moreover, on the swing table 84, the operator""s seat 86 is disposed astride the swing center Sxe2x80x2 of the swing table 84, with a cabin covering the operator""s seat 86 disposed from about the front part to the rear part of the swing table 84, thus constituting the operator""s cab 89. And, to keep an open space in the forward direction of the operator""s seat 86 for better operability, the front end of the operator""s cab 89 rises about vertically from the front end of the swing table 84. The layout and construction of the operator""s cab 89 disposed in the front area as described above also causes interference with the bucket 94.
Conventional arrangement for avoiding such interference between the bucket 94 and the operator""s cab 89 consisted in restricting the rolling motion of the bucket 94 or the turning motion of the second boom section 91, by providing a mechanical safety device such as stopper, etc. or by electrically limiting such motions by using microcomputer, so that the bucket 94 may not get into the area interfering with the operator""s cab 89 when the bucket 94 is wound up. For example, such arrangements are indicated in Provisional Patent Publication No. 4-55530, Provisional Utility Model Publication No. 5-7748, Provisional Utility Model Publication No. 7-4558, and Provisional Utility Model Publication No. 7-38259.
However, electrically controlling the motions of the second boom section 91 and the bucket 94, etc. by using microcomputer led to higher cost because it is necessary to separately provide a control system, and it was also disadvantageous from the structural viewpoint because of the necessity of taking waterproofing and dustproofing measures for the control system, while mechanically avoiding interference by installing a safety device, etc. also increased the cost and led to an increased weight because of the separately installed safety device, etc.
Furthermore, in the case where a extremely-small-swing machine provided with upper and lower rotating shafts 95 and 96 is in the state of deepest excavation as described earlier, the angle xcex8xe2x80x2 against verticality of the axes of the upper rotating shaft 95 and the lower rotating shaft 96 comes close to right angle (small slope angle against the ground), as shown in FIG. 43, namely the two rotating shafts 95 and 96 are in about horizontal position in this state.
As a result, in the case of an excavation of street drain executed by offsetting the bucket 94 with a left-right turn of the second boom section 91, the deepest part of excavation was liable to become shallow, because the bottom end position of the bucket 94 greatly moves upward (amount of increase Yxe2x80x2 indicated in FIG. 43), compared with a case without offset of the bucket 94.
The conventional backhoe device 85 had some defects produced from the structure of the third boom section 92, combined with the orientation of the rotating shafts 95 and 96 described before. Namely, the conventional third boom section 92 has, as shown in FIG. 44, a hinged part 92a with the upper rotating shaft 96 very close to the position where the arm supporting point 93a is disposed, a cylinder protector 92b is provided in extension in the backward direction (when the boom is raised) from this hinged part 92a, the base end of the arm cylinder 98 is supported with a shaft around the rear end of this cylinder protector 92b, and the cylinder protector 92b is disposed in greater part in the axial direction of the arm cylinder 98.
And, the axis of the upper rotating shaft 96 and the arm cylinder 98 are mutually perpendicular and, in the case where the arm 93 and the bucket 94 are offset in left and right directions, the arm cylinder 98 is apart from the greater part of the second boom section 91, except for the tip part of the second boom section 91 supporting the upper rotating shaft 96 with a shaft, as shown in FIG. 45, in plan view. This arm cylinder 98 is therefore in a state protected almost by the third boom section 92 only, although a cylinder protector 92b of the third boom section 92 is provided as mentioned before, and is liable to suffer from damages when it hits against an obstacle, because of a weak supporting and protective structure.
And, because the distance between the hinged part 92a, connecting with the second boom section 91, and the arm supporting point 93a is very short, the arm 93 gets in a state of extending downward almost from the tip of the second boom section 91, when the first boom section 90 to the second boom section 91 are inclined in the forward direction and the arm 93 is further extended downward vertically into a state of deepest excavation. The second boom section 91 in a posture inclined downward in the forward direction is liable to get in touch with an inlet edge 74 of the excavated ditch, as shown in FIG. 46, and not only the second boom section 91 and the third boom section 92 but also said offset cylinder 100 and connecting rod 101, etc. are liable to be damaged.
And, as shown in FIG. 47 and FIG. 48, hardly anything other than the arm 93 and the bucket 94 can get into the excavated ditch, and the depth of excavation cannot be increased so much because it is limited to an amount equal to the total of the respective lengths L2xe2x80x2 and L3xe2x80x2 of the arm 93 and the bucket 94. Moreover, in the case where the excavated earth and sand, etc. are loaded on a dump truck, the machine posture becomes as shown in FIG. 49, and, also in this case, even in the state where the bucket 94 is placed in the farthest position on the third boom section 92, the portion that can be disposed on the load-carrying platform 75 is no more than an mount equal to the total of the lengths L2xe2x80x2 and L3xe2x80x2 of the arm 93 and the bucket 94, because of a short distance from the tip of the second boom section 91 to the base end of the arm 93. As a result, the bucket 94 does not reach the front part of the load-carrying platform 75, in the case where the earth and sand are loaded from the backward direction of the load-carrying platform 75, making it necessary to move the working machine to the front part each time when the earth and sand are loaded on that part.
Furthermore, as shown in FIG. 40, when the first boom section 90 is raised to the highest position, the second boom section 91 is displaced in a way to be inclined forward, and the arm 93 is disposed about in vertical position and, for that reason, the area surrounded by the second boom section 91, the third boom section 92, the arm 93 and the line connecting between the bottom end of the second boom section 91 and the bottom end of the arm 93, in which is stored the bucket 94 in the state where the bucket 94 is wound up, is in about a triangle shape and very narrow. Consequently, in case this bucket 94 is wound up in a state having large excavated materials such as asphalt, etc. in it, there was a fear of breaking the second boom section 91, the third boom section 92 or the arm 93 by hitting against the excavated material protruding from the bucket 94.
In addition to such problems with working arm device and operator""s cab represented by the backhoe device 85, the conventional extremely-small-swing working machine, which is constructed by disposing a muffler and an exhaust pipe for discharging exhaust air from the muffler to outside in the bonnet so as to discharge the exhaust air in the backward direction from a low position such as swing table, etc. located below the bonnet, presented problems such as discomfort caused by the exhaust air to workers working near the extremely-small-swing working machine in the direction of discharge of the exhaust air, drop of working efficiency with shielding of visual field, or withering of trees and plants in the neighborhood of the extremely-small-swing working machine, etc.
An extremely-small-swing working machine according to the present invention is constructed, basically, by providing an operator""s cab on a swing table and also providing, on one side of left and right, with reference to the position and orientation of the operator""s cab, a working arm device composed of a first boom section on the swing table in a way to turn freely from front bottom to rear top, a second boom section connected to the turning tip of the first boom in a way to turn freely to left and right through a lower rotating shaft, a third boom section connected to the second boom section in a way to turn freely, in opposite direction, synchronizing with left-right turning of the second boom section, an arm connected to the third boom section in a way to turn freely up and down in the longitudinal direction, and a working attachment connected to the tip of the arm, in such a way as to make the working attachment move to left and right with left-right turning of the second boom section, and has characteristics providing the effects meeting the respective purposes to be described below.
As the first point, the extremely-small-swing working machine according to the present invention is constructed in a way to avoid any contact between the working attachment and the operator""s cab, over the entire working range of the working attachment, without restricting or controlling the motions of the working attachment, to reduce the cost and weight.
To achieve such objective, the present invention will be constructed in such a way that, in the case where the first boom section is positioned at the turning limit at rear top, on the working arm device, one end closer to the arm, of the two ends of its lower rotating shaft, may come in a position higher than the other end. As a result, when the working attachment is moved to left and right, the portion from the second boom section to the working attachment will move to the arm side around the lower rotating shaft, and gets away from the operator""s cab on the side opposite to the arm in side view.
Moreover, also on the working arm device, construction will be made in such a way that, when the first boom section is positioned at the turning limit at rear top, the angle formed by the axis of the lower rotating shaft and the front end face of the operator""s cab becomes about right angle in side view. As a result, when the working attachment is moved to left and right, the portion from the second boom section to the working attachment will turn in parallel to the front end face of the operator""s cab around the lower rotating shaft.
Such construction of the working arm system enables to prevent interference between the operator""s cab and the working attachment, especially in the case where the working attachment is moved to left and right toward the operator""s cab.
On the other hand, as for the construction of the operator""s cab, the operator""s seat in the operator""s cab will be disposed in the backward direction from the swing center of the swing table and, at the same time, the operator""s cab will be disposed at a position closer to the rear part on the swing table. This makes it possible to secure an open space in the front part of the operator""s cab, operate the working attachment freely in that open space, and thus avoid interference with the operator""s cab.
By utilizing, on the swing table, the open space in the forward direction which becomes available by disposing the operator""s cab in the rear part, the oil feed port and the battery are disposed at a position not interfering with the working attachment in front of the operator""s cab on the swing table, and those oil feed port and battery are covered by a resin hood. By disposing those members in this position, it becomes possible to secure an open space on the left and right sides of the operator""s cab. The rear end face of the hood can be utilized directly as dashboard (front panel), without putting any obstacle to the operator""s sight. The hood made of resin, free from any fear of rusting or peeling of paint even with adhesion of earth and sand or water, etc., can be manufactured at low cost.
Next, the second point is that the extremely-small-swing working machine according to the present invention is constructed in such a way that, in the case where the first boom section is positioned at the turning limit at rear top, both the first boom section and the second boom section are inclined rearward in the shape of a slope, to prevent the front part of the working arm device from protruding too much in the forward direction from the swing table, at the time of raising and folding of the working arm device, and that the angle against verticality of the second boom section is smaller than the angle against verticality of the first boom section to prevent the rear end of the working arm device from protruding too much in the backward direction from the swing table, to enable extremely-small swing.
Moreover, on the working arm device having a boom construction as described above, will be provided a rod forming a link parallel to the second boom section during a left-right turning of the second boom section between the first boom section and the third boom section, and at least one end of this rod will be connected to an area near the rear end of the third boom section, when said first boom section is positioned at the turning limit at rear top. As a result, even if the rod protrudes in the forward direction, in side view, from the second boom section at the lower half of the second boom section, when the first boom section is located at the turning limit at rear top in the same way as above, it overlaps with the second boom section at least at the upper half. Therefore, even if the first boom section is inclined in the forward direction for excavation work, etc., the rod does not protrude downward from the front half part of the second boom section which gets in a state of downward slope in the forward direction, and it becomes possible to avoid contact between the rod and the ground face even when the second boom section gets in contact with the ground.
As a third point, it is desirable, in an underground excavation work, to secure a deepest possible excavation, in the case where the working arm device is used as backhoe device by using a bucket as working attachment, for example. The present invention will therefore be constructed in such a way that, in the case where the first boom section is positioned at the turning limit at front bottom, the orientation of the axis of the lower rotating shaft and the axis of the upper rotating shaft may be about vertical. This will make it possible, in the case where the first boom section is positioned at the turning limit at front bottom, in the state where the working attachment is moved to left and right by turning the second boom section to left and right, to secure the deepest excavation point almost equal to that without offset, and perform excavation of a deep street drain, in the case where the height of the working attachment is hardly higher than the state without offset and, therefore, an excavation work of street drain, etc. is executed by using a bucket as working attachment.
Furthermore, the third boom section is formed in a way to extend downward, when the first boom section is positioned at the turning limit at front bottom, and its breadth is formed smaller than the breadth of the working attachment, making it possible to perform deep excavation with a depth equal to the total lengths of the third boom section, the arm and the bucket, while the side face of the ditch is formed with the side face of the bucket and there is no fear of destroying the ditch by contact with the third boom section.
The fourth point is to incline the first boom section upward in the forward direction and, in the state in which the arm is extended downward vertically, lower the highest position of the working arm device, so as to avoid obstacle over the working position as much as possible, for ground surface treatment, etc. by the attachment. For that purpose, the present invention will be constructed in such a way that the turning fulcrum of the arm on the third boom section is positioned above the axial extension line of the upper rotating shaft. This makes it possible to moderate the angle formed by the second boom section and the third boom section, when the working arm device is put in said posture for ground surface treatment, etc., and thus lower the position of the highest part of the working arm device.
Consequently, even in the case where there is any obstacle at a fairly low position above the working position, it becomes possible to execute work such as ground surface treatment, etc. with the working attachment.
The fifth point concerns protection of the working arm device. In the first place, it will be so constructed that, when the first boom section is positioned at the turning limit at rear top and the arm is wound up to the maximum, the arm and the second boom section are disposed about parallel to each other. Therefore, even when a bucket is used as working attachment for example and that the excavated asphalt blocks, etc. scooped into the bucket protrude from the bucket, an open space in longitudinal direction is secured between the second boom section and the arm in front of it, and the asphalt blocks, etc. hardly get in touch with the second boom section even if the tip of the bucket wound up to the maximum comes closer to the second boom section, thus enabling to avoid damage to the second boom section.
Still more, the upper rotating shaft is made to move along (the actuator) about in parallel to it in the greater part in the axial direction of the aim-operating actuator provided between the arm and the third boom section, while part of the second boom section is installed along the actuator, as radial bearing of the upper rotating shaft over about the entire length of the upper rotating shaft. As a result, since there exists a radial bearing of the second boom section along the arm-operating actuator even during a left-right turning of the second arm, the arm-operating actuator is solidly supported and is not easily damaged even in case it is hit by some obstacle.
And, the sixth point concerns the exhaust muffler and the exhaust pipe. In the present invention, an exhaust muffler is installed outside the bonnet covering the engine serving as motor loaded on the swing table, to avoid that the cool air from the radiator or oil cooler, etc., incorporated in the bonnet, be warmed by the heat of the muffler and lose its cooling effects. In addition, the terminal end of the exhaust pipe extended from the exhaust muffler is made to protrude above the operator""s cab, to discharge the exhaust air from the upper part of the operator""s cab and thus turn the exhaust air away from people working near the working machine and trees and plants, etc. in the surrounding area.